In thermal printing, it is generally well known to render images by heating and pressing one or more donor materials such as a dye, colorant or other coating against a receiver medium. The donor materials are provided in sized donor patches on a movable web known as a donor ribbon. The donor patches are organized on the ribbon into donor sets, each set containing all of the donor patches that are to be used to record an image on the receiver medium. For full color images, multiple color dye patches can be used, such as yellow, magenta and cyan donor dye patches. Arrangements of other color patches can be used in like fashion within a donor set. Additionally, each donor set can include an overcoat or sealant layer.
Thermal printers offer a wide range of advantages in photographic printing including the provision of truly continuous tone scale variation and the ability to deposit, as a part of the printing process a protective overcoat layer to protect the images formed thereby from mechanical and environmental damage. Accordingly, the most popular photographic kiosks and home photo printers currently use thermal printing technology.
There is, however, a desire to have such printers print images at a faster rate. This requires that such thermal printers transfer donor material at a higher rate of speed, which in turn, allows a reduced time period for donor material transfer—per picture image element (pixel). Accordingly, the thermal load that must be applied to cause donor material to be transferred to the receiver medium must be delivered in this reduced time period. This requires an increase in the temperatures that are delivered to the donor ribbon. These increased temperatures can negatively impact the printing process.
What is needed therefore is a control system for use with a thermal printer that allows a high rate of printing while preventing overheating of the printhead particularly during extended printing jobs.
What is also needed is a control system that can control such temperatures without requiring extended print delays between individual images within the printing order as consumers and even some retailers can confuse such delays with an end of the process of printing the print order and thus can erroneously package and deliver only those images that were printed before the extended print delay.